Thermal Comfort in Indoor Environments

Thermal comfort in indoor environments refers to the state of mind that expresses satisfaction with the surrounding thermal conditions. It emerges from complex interactions among air temperature, radiant temperature, humidity, air movement, clothing insulation and metabolic rate. In recent decades, research has shifted from purely mechanistic heat-balance approaches towards more holistic frameworks that account for adaptive behaviours, individual variability and dynamic conditions. Practically, thermal comfort underpins occupant well-being, health, productivity and building energy demand. In warm climates, passive cooling strategies and adaptive control can reduce reliance on mechanical systems, while in cool climates, personalised heating and improved envelope design can enhance comfort without excessive energy use. Global trends such as urban heat islands, extreme weather events and decarbonisation targets have elevated thermal comfort to a critical factor in building design, operation and policy. Integrating occupant feedback, advanced sensing and predictive modelling now enables finer control of indoor climates, paving the way for comfort strategies that simultaneously optimise energy, health and resilience.

Research from Nature Portfolio

Recent studies have leveraged large-scale field data to refine adaptive comfort models for diverse climate zones. One investigation deployed in-situ sensors and occupant surveys across multiple urban regions to demonstrate that conventional fixed thresholds often misrepresent comfort in naturally ventilated settings. The study proposed a revised adaptive algorithm that incorporates real-time behavioural adjustments such as clothing changes and window opening, resulting in a 20 % improvement in predictive accuracy over standard guidelines. Another contribution combined computational fluid dynamics with thermophysiological simulations to predict transient thermal sensations in mixed-mode buildings under heat-wave scenarios. By integrating human heat–balance models with detailed airflow patterns, this work pinpointed hotspots of discomfort and informed dynamic façade control strategies that cut peak cooling loads by up to 30 % while maintaining occupant satisfaction. These advances underscore the benefit of coupling occupant-centred data streams with advanced physics-based modelling to achieve robust comfort outcomes in a changing climate.

Thermal Comfort in Indoor Environments publication trend

The graph below shows the total number of articles in thermal comfort in indoor environments across all publications each year (not limited to Nature Index journals).

Technical terms

Operative temperature: A unified index combining air and mean radiant temperature to represent the uniform temperature of an imaginary environment in which an occupant’s heat loss matches that in the actual non-uniform environment.

Predicted Mean Vote (PMV): A heat-balance based index predicting the average thermal sensation of a large group of people on a seven-point scale from cold (–3) to hot (+3).

Predicted Percentage of Dissatisfied (PPD): A statistical expression linked to PMV that estimates the proportion of occupants likely to feel thermally dissatisfied in a given environment.

Adaptive thermal comfort model: A framework recognising that occupants adapt physiologically and behaviourally—through clothing adjustments, activity changes and control of openings—so acceptable indoor temperatures can vary with outdoor climatic conditions.

References

1. Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance. Environmental Health Perspectives (2012).
2. CBE Thermal Comfort Tool: Online tool for thermal comfort calculations and visualizations. SoftwareX (2020).
3. Thermophysiological models and their applications: A review. Building and Environment (2016).